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Human cells–Nature's Nanobots Human cells–Nature′s Nanobots The average adult human body contains somewhere between 50 to 100 trillion cells. So where do these trillions of tiny machines come from? If you trace them back far enough, they all originate from embryonic stem cells. Do you know, it is impossible to sneeze with your eyes open ! Quite simply, it′s a reflex. The nose and eyes are linked by cranial nerves, so the stimulation from the sneeze travels up one nerve to the brain, then down another nerve to the eyelids, triggering a blink for most people. Let′s read on to see more amazing facts of human body that make our body what it is.

Learning Objectives

After completing the topic, the student will be able to:

  • Define the term “Human Physiology” and explore how human body works.
  • Explore the concepts of cellular differentiation, totipotency and pluripotency.
  • List the specialized cells of the human body and illustrate the four general classes of human tissues.
  • Name the different organ and organ systems of the human body and analyze how they work together as one unit and summarize the functions of human body systems.
  • Define homeostasis, and explore its general characteristics.
  • Understand the concepts of positive and negative feed–back mechanisms.
  • Identify some of the risk factors associated with homeostatic imbalance.
  • Understand the concepts of diffusion and osmosis and identify in which physiological process these two phenomena occur in the human body.
Scope of Human Physiology Scope of Human Physiology Human physiology is the science of the mechanical, physical, bioelectrical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed.
Introduction

Physiology is the study of how living organisms work. Human physiology is the science of the mechanical, physical, and biochemical functions of normal humans or human tissues or organs. Human Physiology focuses principally at the level of organs and systems.

Most aspects of human physiology are closely homologous to corresponding aspects of animal physiology, and animal experimentation has provided much of the foundation of physiological knowledge. Anatomy and physiology are closely related fields of study: anatomy, the study of form, and physiology, the study of function, are intrinsically related and are studied in tandem as part of a medical curriculum.

In unicellular organisms, all vital processes occur in a single cell. As the evolution of multicellular organisms has progressed, various cell groups organized into tissues and organs have taken over particular functions.

In humans and other vertebrate animals, the specialized cell groups include a gastrointestinal system to digest and absorb food; a respiratory system to take up oxygen and eliminate carbon dioxide; a urinary system to remove wastes, cardiovascular system to distribute nutrients, oxygen, and the products of metabolism; a reproductive system to perpetuate the species; and nervous and endocrine systems to coordinate and integrate the functions of the other systems.

Mechanisms of Human Physiology Human physiology includes the study of individual molecules–for example, how a particular nerve′s cell shape and electrical properties allow it to function as a signal molecule where cell communication.
Integrated functions

As applied to human beings, its scope is extremely broad. At one end of the spectrum, it includes the study of individual molecules–for example, how a particular protein’s shape and electrical properties allow it to function as a channel for ions to move into or out of a cell.

At the other end, it is concerned with complex processes that depend on the integrated functions of many organs in the body–for example, how the heart, kidneys, and several glands all work together to cause the excretion of more sodium in the urine when a person has eaten salty food.

Physiologists are interested in function and integration– how parts of the body work together at various levels of organization and, most importantly, in the entire organism. Thus, even when physiologists study parts of organisms, all the way down to individual molecules, the intention is ultimately to apply the information they gain to the function of the whole body.

In this regard, a very important point must be made about the present and future status of physiology. It is easy for a student to gain the impression from reading the content that almost everything is known about the subject, but nothing could be farther from the truth for physiology. Many areas of function are still only poorly understood, such as how the workings of the brain produce conscious, thought and memory.